Transfinite sequence
From HandWiki
of elements of a given set $ X $
A mapping of an interval $ [ 0, \beta ) $ of (transfinite) ordinal numbers into $ X $( cf. also Ordinal number). By an element, or term, of the transfinite sequence $ f: [ 0, \beta ) \rightarrow X $ is meant an ordered pair $ ( \alpha , x) $, where $ \alpha \in [ 0, \beta ) $ and $ x= f( \alpha ) $; this term is often denoted by $ x _ \alpha $.
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